SQL PRIMARY KEY Constraint - W3Schools
SQL PRIMARY KEY Constraint The PRIMARY KEY constraint is used to uniquely identify each record in a table. Primary keys must contain unique values, and cannot contain NULL values. …
Create Primary Keys in SQL Server - SQL Server | Microsoft Learn
Nov 18, 2025 · Creating a primary key in an existing table requires ALTER permission on the table. In Object Explorer, right-click the table to which you want to add a unique constraint, and …
SQL Query to Create Table With a Primary Key - GeeksforGeeks
Jul 23, 2025 · In this article, we will explain the importance of primary keys, demonstrate how to create and manage them with SQL queries, and provide practical examples with outputs to …
SQL Primary Key
In this tutorial, you will learn how to use the SQL PRIMARY KEY constraint to add a primary key to the table.
SQL Server Create Table With Primary Key - SQL Server Guides
Nov 17, 2025 · Understanding primary key creation is fundamental to building robust, scalable databases. Today, I’ll share my comprehensive guide on creating tables with primary keys in …
How to Add a Primary Key to an Existing SQL Table - dbvis.com
May 13, 2025 · Learn to add a primary key to existing SQL tables with ALTER TABLE in SQL Server, MySQL, PostgreSQL, and Oracle.
SQL PRIMARY KEY: How to Create & Add to Existing Table
Jun 28, 2024 · This tutorial covers SQL Primary Key definitions, rules, How to add a primary key to an existing table in SQL, interesting facts, and more with detailed examples.
SQL Server: Primary Keys - TechOnTheNet
Learn how to create, change, drop, disable, and enable a primary key in SQL Server (Transact-SQL) with syntax and examples. In SQL Server (Transact-SQL), a primary key is a single field …
How to Create a Primary Key in SQL Server (T-SQL Examples)
Aug 5, 2019 · This article demonstrates how to create a primary key in SQL Server when creating a table using Transact-SQL. A primary key is one or more columns that have been configured …
PostgreSQL - Create Table with Primary Key - Examples
In this tutorial, we will demonstrate how to create tables with primary keys using various scenarios, including single-column keys, composite keys, adding a primary key to an existing …